It is proposed to utilize a newly devised technique for separation of pre-existing histones attached to parental DNA from newly synthesized ones attached to newly replicated DNA, to study if certain premitotic modifications occur on pre-existing parental or newly synthesized histones. In addition to a more thorough study of the two histone moieties, we propose to study the strandedness of premitotic histone N-methylation, phosphorylation and N-acetylation. BIBLIOGRAPHIC REFERENCES: Byvoet, Paul and David F. Sayre: Mechanism of stimulatinon of In Vitro Histone Methylation in Nuclei by Polycations. Proceedings of American Association of Biological Chemists, 1976 (abstract). Byvoet, Paul and David F. Sayre: Stimulation of Histone Methylation by Intercalating Anti-tumor Drugs. Proceedings of American Association for Cancer Research, 1976 (abstract).